1. Field of the Invention
The present invention relates to an optical device in which an optically transparent substance is hermetically enclosed in the space between two flat plates which are transparent to an employed range of wavelengths, and which is capable of transmitting a light flux without substantially impairing the optical performance of the light flux, by varying the relative angle between the two flat plates, i.e., an apex angle. More particularly, the present invention relates to an arrangement for restraining undesired light from occurring in an optical device having a structure for refracting a light flux at a desired angle, for example, an image stabilizing optical system which is disposed in a particular portion of the photographic system of a photographic camera, a video camera or the like to correct an image shake occurring due to a vibration of the photographic system.
2. Description of the Related Art
Conventionally, various kinds of optical devices capable of arbitrarily varying the optical performance of a transmitted light flux have been proposed. Such an optical device includes two transparent flat plates and an optically transparent substance, such as a liquid or a silicone rubber, which is hermetically enclosed in the space between the two transparent flat plates to form a variable angle prism, and is arranged to vary the angle between the two flat plates (i.e., the degree of parallelism) by an external urging force, thereby realizing the aforesaid capability to arbitrarily vary the optical performance of a transmitted light flux.
FIGS. 24 and 25 are schematic, cross-sectional views of an optical device which is proposed in, for example, Japanese Patent Publication No. Sho 41-11906. The optical device shown in FIGS. 24 and 25 includes two transparent flat plates 1 disposed in opposed relation to each other, a flexible, tubular connecting member 2 which circumferentially holds the two transparent flat plates 1, and a transparent liquid 3 which is hermetically enclosed in the space defined between the two transparent flat plates 1 by the flexible, tubular connecting member 2. In the optical device having the above-described arrangement, an incident light flux h is deflected by a predetermined angle, and the thus-deflected light flux is made to exit from the optical device. The optical device constitutes a variable angle prism capable of arbitrarily controlling its apex angle by varying the relative angle between the two flat plates 1 by an external urging force as shown in FIG. 25, thereby deflecting the incident light flux h by the predetermined angle and causing the thus-deflected light flux to exit from the optical device.
However, the conventional optical device has the problem that a ghost occasionally occurs and degrades image quality. The analysis performed by the inventors of the present invention makes it clear that the ghost is caused by a reflection occurring at the interface between either of the flat plates 1 and the transparent substance 3 hermetically enclosed in the optical device.
The inventors have discovered further problems involved in the conventional optical device.
One problem is that if an optical device having the aforesaid conventional arrangement using colored flat plates is adopted in an apparatus for forming an image by white light, correct color reproduction is difficult to achieve.
Another problem is that the quantity of light is somewhat smaller after the transmission of the light through the optical device than before the transmission.